/****************************************************************
 *
 * The author of this software is David M. Gay.
 *
 * Copyright (c) 1991, 2000, 2001 by Lucent Technologies.
 * Copyright (C) 2002, 2005, 2006, 2007, 2008, 2010, 2012 Apple Inc.
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHOR NOR LUCENT MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 *
 ***************************************************************/

/* Please send bug reports to David M. Gay (dmg at acm dot org,
 * with " at " changed at "@" and " dot " changed to ".").    */

/* On a machine with IEEE extended-precision registers, it is
 * necessary to specify double-precision (53-bit) rounding precision
 * before invoking strtod or dtoa.  If the machine uses (the equivalent
 * of) Intel 80x87 arithmetic, the call
 *    _control87(PC_53, MCW_PC);
 * does this with many compilers.  Whether this or another call is
 * appropriate depends on the compiler; for this to work, it may be
 * necessary to #include "float.h" or another system-dependent header
 * file.
 */

#include "flutter/sky/engine/wtf/dtoa.h"

#include "flutter/sky/engine/wtf/CPU.h"
#include "flutter/sky/engine/wtf/MathExtras.h"
#include "flutter/sky/engine/wtf/ThreadingPrimitives.h"
#include "flutter/sky/engine/wtf/Vector.h"

namespace WTF {

Mutex* s_dtoaP5Mutex;

typedef union {
  double d;
  uint32_t L[2];
} U;

#if CPU(BIG_ENDIAN) || CPU(MIDDLE_ENDIAN)
#define word0(x) (x)->L[0]
#define word1(x) (x)->L[1]
#else
#define word0(x) (x)->L[1]
#define word1(x) (x)->L[0]
#endif
#define dval(x) (x)->d

#define Exp_shift 20
#define Exp_shift1 20
#define Exp_msk1 0x100000
#define Exp_msk11 0x100000
#define Exp_mask 0x7ff00000
#define P 53
#define Bias 1023
#define Emin (-1022)
#define Exp_1 0x3ff00000
#define Exp_11 0x3ff00000
#define Ebits 11
#define Frac_mask 0xfffff
#define Frac_mask1 0xfffff
#define Ten_pmax 22
#define Bletch 0x10
#define Bndry_mask 0xfffff
#define Bndry_mask1 0xfffff
#define LSB 1
#define Sign_bit 0x80000000
#define Log2P 1
#define Tiny0 0
#define Tiny1 1
#define Quick_max 14
#define Int_max 14

#define rounded_product(a, b) a *= b
#define rounded_quotient(a, b) a /= b

#define Big0 (Frac_mask1 | Exp_msk1 * (DBL_MAX_EXP + Bias - 1))
#define Big1 0xffffffff

#if CPU(X86_64)
// FIXME: should we enable this on all 64-bit CPUs?
// 64-bit emulation provided by the compiler is likely to be slower than dtoa
// own code on 32-bit hardware.
#define USE_LONG_LONG
#endif

#ifndef USE_LONG_LONG
/* The following definition of Storeinc is appropriate for MIPS processors.
 * An alternative that might be better on some machines is
 *  *p++ = high << 16 | low & 0xffff;
 */
static ALWAYS_INLINE uint32_t* storeInc(uint32_t* p,
                                        uint16_t high,
                                        uint16_t low) {
  uint16_t* p16 = reinterpret_cast<uint16_t*>(p);
#if CPU(BIG_ENDIAN)
  p16[0] = high;
  p16[1] = low;
#else
  p16[1] = high;
  p16[0] = low;
#endif
  return p + 1;
}
#endif

struct BigInt {
  BigInt() : sign(0) {}
  int sign;

  void clear() {
    sign = 0;
    m_words.clear();
  }

  size_t size() const { return m_words.size(); }

  void resize(size_t s) { m_words.resize(s); }

  uint32_t* words() { return m_words.data(); }

  const uint32_t* words() const { return m_words.data(); }

  void append(uint32_t w) { m_words.append(w); }

  Vector<uint32_t, 16> m_words;
};

static void multadd(BigInt& b, int m, int a) /* multiply by m and add a */
{
#ifdef USE_LONG_LONG
  unsigned long long carry;
#else
  uint32_t carry;
#endif

  int wds = b.size();
  uint32_t* x = b.words();
  int i = 0;
  carry = a;
  do {
#ifdef USE_LONG_LONG
    unsigned long long y = *x * (unsigned long long)m + carry;
    carry = y >> 32;
    *x++ = (uint32_t)y & 0xffffffffUL;
#else
    uint32_t xi = *x;
    uint32_t y = (xi & 0xffff) * m + carry;
    uint32_t z = (xi >> 16) * m + (y >> 16);
    carry = z >> 16;
    *x++ = (z << 16) + (y & 0xffff);
#endif
  } while (++i < wds);

  if (carry)
    b.append((uint32_t)carry);
}

static int hi0bits(uint32_t x) {
  int k = 0;

  if (!(x & 0xffff0000)) {
    k = 16;
    x <<= 16;
  }
  if (!(x & 0xff000000)) {
    k += 8;
    x <<= 8;
  }
  if (!(x & 0xf0000000)) {
    k += 4;
    x <<= 4;
  }
  if (!(x & 0xc0000000)) {
    k += 2;
    x <<= 2;
  }
  if (!(x & 0x80000000)) {
    k++;
    if (!(x & 0x40000000))
      return 32;
  }
  return k;
}

static int lo0bits(uint32_t* y) {
  int k;
  uint32_t x = *y;

  if (x & 7) {
    if (x & 1)
      return 0;
    if (x & 2) {
      *y = x >> 1;
      return 1;
    }
    *y = x >> 2;
    return 2;
  }
  k = 0;
  if (!(x & 0xffff)) {
    k = 16;
    x >>= 16;
  }
  if (!(x & 0xff)) {
    k += 8;
    x >>= 8;
  }
  if (!(x & 0xf)) {
    k += 4;
    x >>= 4;
  }
  if (!(x & 0x3)) {
    k += 2;
    x >>= 2;
  }
  if (!(x & 1)) {
    k++;
    x >>= 1;
    if (!x)
      return 32;
  }
  *y = x;
  return k;
}

static void i2b(BigInt& b, int i) {
  b.sign = 0;
  b.resize(1);
  b.words()[0] = i;
}

static void mult(BigInt& aRef, const BigInt& bRef) {
  const BigInt* a = &aRef;
  const BigInt* b = &bRef;
  BigInt c;
  int wa, wb, wc;
  const uint32_t* x = 0;
  const uint32_t* xa;
  const uint32_t* xb;
  const uint32_t* xae;
  const uint32_t* xbe;
  uint32_t* xc;
  uint32_t* xc0;
  uint32_t y;
#ifdef USE_LONG_LONG
  unsigned long long carry, z;
#else
  uint32_t carry, z;
#endif

  if (a->size() < b->size()) {
    const BigInt* tmp = a;
    a = b;
    b = tmp;
  }

  wa = a->size();
  wb = b->size();
  wc = wa + wb;
  c.resize(wc);

  for (xc = c.words(), xa = xc + wc; xc < xa; xc++)
    *xc = 0;
  xa = a->words();
  xae = xa + wa;
  xb = b->words();
  xbe = xb + wb;
  xc0 = c.words();
#ifdef USE_LONG_LONG
  for (; xb < xbe; xc0++) {
    if ((y = *xb++)) {
      x = xa;
      xc = xc0;
      carry = 0;
      do {
        z = *x++ * (unsigned long long)y + *xc + carry;
        carry = z >> 32;
        *xc++ = (uint32_t)z & 0xffffffffUL;
      } while (x < xae);
      *xc = (uint32_t)carry;
    }
  }
#else
  for (; xb < xbe; xb++, xc0++) {
    if ((y = *xb & 0xffff)) {
      x = xa;
      xc = xc0;
      carry = 0;
      do {
        z = (*x & 0xffff) * y + (*xc & 0xffff) + carry;
        carry = z >> 16;
        uint32_t z2 = (*x++ >> 16) * y + (*xc >> 16) + carry;
        carry = z2 >> 16;
        xc = storeInc(xc, z2, z);
      } while (x < xae);
      *xc = carry;
    }
    if ((y = *xb >> 16)) {
      x = xa;
      xc = xc0;
      carry = 0;
      uint32_t z2 = *xc;
      do {
        z = (*x & 0xffff) * y + (*xc >> 16) + carry;
        carry = z >> 16;
        xc = storeInc(xc, z, z2);
        z2 = (*x++ >> 16) * y + (*xc & 0xffff) + carry;
        carry = z2 >> 16;
      } while (x < xae);
      *xc = z2;
    }
  }
#endif
  for (xc0 = c.words(), xc = xc0 + wc; wc > 0 && !*--xc; --wc) {
  }
  c.resize(wc);
  aRef = c;
}

struct P5Node {
  WTF_MAKE_NONCOPYABLE(P5Node);
  WTF_MAKE_FAST_ALLOCATED;

 public:
  P5Node() {}
  BigInt val;
  P5Node* next;
};

static P5Node* p5s;
static int p5sCount;

static ALWAYS_INLINE void pow5mult(BigInt& b, int k) {
  static int p05[3] = {5, 25, 125};

  if (int i = k & 3)
    multadd(b, p05[i - 1], 0);

  if (!(k >>= 2))
    return;

  s_dtoaP5Mutex->lock();
  P5Node* p5 = p5s;

  if (!p5) {
    /* first time */
    p5 = new P5Node;
    i2b(p5->val, 625);
    p5->next = 0;
    p5s = p5;
    p5sCount = 1;
  }

  int p5sCountLocal = p5sCount;
  s_dtoaP5Mutex->unlock();
  int p5sUsed = 0;

  for (;;) {
    if (k & 1)
      mult(b, p5->val);

    if (!(k >>= 1))
      break;

    if (++p5sUsed == p5sCountLocal) {
      s_dtoaP5Mutex->lock();
      if (p5sUsed == p5sCount) {
        ASSERT(!p5->next);
        p5->next = new P5Node;
        p5->next->next = 0;
        p5->next->val = p5->val;
        mult(p5->next->val, p5->next->val);
        ++p5sCount;
      }

      p5sCountLocal = p5sCount;
      s_dtoaP5Mutex->unlock();
    }
    p5 = p5->next;
  }
}

static ALWAYS_INLINE void lshift(BigInt& b, int k) {
  int n = k >> 5;

  int origSize = b.size();
  int n1 = n + origSize + 1;

  if (k &= 0x1f)
    b.resize(b.size() + n + 1);
  else
    b.resize(b.size() + n);

  const uint32_t* srcStart = b.words();
  uint32_t* dstStart = b.words();
  const uint32_t* src = srcStart + origSize - 1;
  uint32_t* dst = dstStart + n1 - 1;
  if (k) {
    uint32_t hiSubword = 0;
    int s = 32 - k;
    for (; src >= srcStart; --src) {
      *dst-- = hiSubword | *src >> s;
      hiSubword = *src << k;
    }
    *dst = hiSubword;
    ASSERT(dst == dstStart + n);

    b.resize(origSize + n + !!b.words()[n1 - 1]);
  } else {
    do {
      *--dst = *src--;
    } while (src >= srcStart);
  }
  for (dst = dstStart + n; dst != dstStart;)
    *--dst = 0;

  ASSERT(b.size() <= 1 || b.words()[b.size() - 1]);
}

static int cmp(const BigInt& a, const BigInt& b) {
  const uint32_t *xa, *xa0, *xb, *xb0;
  int i, j;

  i = a.size();
  j = b.size();
  ASSERT(i <= 1 || a.words()[i - 1]);
  ASSERT(j <= 1 || b.words()[j - 1]);
  if (i -= j)
    return i;
  xa0 = a.words();
  xa = xa0 + j;
  xb0 = b.words();
  xb = xb0 + j;
  for (;;) {
    if (*--xa != *--xb)
      return *xa < *xb ? -1 : 1;
    if (xa <= xa0)
      break;
  }
  return 0;
}

static ALWAYS_INLINE void diff(BigInt& c,
                               const BigInt& aRef,
                               const BigInt& bRef) {
  const BigInt* a = &aRef;
  const BigInt* b = &bRef;
  int i, wa, wb;
  uint32_t* xc;

  i = cmp(*a, *b);
  if (!i) {
    c.sign = 0;
    c.resize(1);
    c.words()[0] = 0;
    return;
  }
  if (i < 0) {
    const BigInt* tmp = a;
    a = b;
    b = tmp;
    i = 1;
  } else
    i = 0;

  wa = a->size();
  const uint32_t* xa = a->words();
  const uint32_t* xae = xa + wa;
  wb = b->size();
  const uint32_t* xb = b->words();
  const uint32_t* xbe = xb + wb;

  c.resize(wa);
  c.sign = i;
  xc = c.words();
#ifdef USE_LONG_LONG
  unsigned long long borrow = 0;
  do {
    unsigned long long y = (unsigned long long)*xa++ - *xb++ - borrow;
    borrow = y >> 32 & (uint32_t)1;
    *xc++ = (uint32_t)y & 0xffffffffUL;
  } while (xb < xbe);
  while (xa < xae) {
    unsigned long long y = *xa++ - borrow;
    borrow = y >> 32 & (uint32_t)1;
    *xc++ = (uint32_t)y & 0xffffffffUL;
  }
#else
  uint32_t borrow = 0;
  do {
    uint32_t y = (*xa & 0xffff) - (*xb & 0xffff) - borrow;
    borrow = (y & 0x10000) >> 16;
    uint32_t z = (*xa++ >> 16) - (*xb++ >> 16) - borrow;
    borrow = (z & 0x10000) >> 16;
    xc = storeInc(xc, z, y);
  } while (xb < xbe);
  while (xa < xae) {
    uint32_t y = (*xa & 0xffff) - borrow;
    borrow = (y & 0x10000) >> 16;
    uint32_t z = (*xa++ >> 16) - borrow;
    borrow = (z & 0x10000) >> 16;
    xc = storeInc(xc, z, y);
  }
#endif
  while (!*--xc)
    wa--;
  c.resize(wa);
}

static ALWAYS_INLINE void d2b(BigInt& b, U* d, int* e, int* bits) {
  int de, k;
  uint32_t* x;
  uint32_t y, z;
  int i;
#define d0 word0(d)
#define d1 word1(d)

  b.sign = 0;
  b.resize(1);
  x = b.words();

  z = d0 & Frac_mask;
  d0 &= 0x7fffffff; /* clear sign bit, which we ignore */
  if ((de = (int)(d0 >> Exp_shift)))
    z |= Exp_msk1;
  if ((y = d1)) {
    if ((k = lo0bits(&y))) {
      x[0] = y | (z << (32 - k));
      z >>= k;
    } else
      x[0] = y;
    if (z) {
      b.resize(2);
      x[1] = z;
    }

    i = b.size();
  } else {
    k = lo0bits(&z);
    x[0] = z;
    i = 1;
    b.resize(1);
    k += 32;
  }
  if (de) {
    *e = de - Bias - (P - 1) + k;
    *bits = P - k;
  } else {
    *e = 0 - Bias - (P - 1) + 1 + k;
    *bits = (32 * i) - hi0bits(x[i - 1]);
  }
}
#undef d0
#undef d1

static const double tens[] = {1e0,  1e1,  1e2,  1e3,  1e4,  1e5,  1e6,  1e7,
                              1e8,  1e9,  1e10, 1e11, 1e12, 1e13, 1e14, 1e15,
                              1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22};

static const double bigtens[] = {1e16, 1e32, 1e64, 1e128, 1e256};

#define Scale_Bit 0x10
#define n_bigtens 5

static ALWAYS_INLINE int quorem(BigInt& b, BigInt& S) {
  size_t n;
  uint32_t* bx;
  uint32_t* bxe;
  uint32_t q;
  uint32_t* sx;
  uint32_t* sxe;
#ifdef USE_LONG_LONG
  unsigned long long borrow, carry, y, ys;
#else
  uint32_t borrow, carry, y, ys;
  uint32_t si, z, zs;
#endif
  ASSERT(b.size() <= 1 || b.words()[b.size() - 1]);
  ASSERT(S.size() <= 1 || S.words()[S.size() - 1]);

  n = S.size();
  ASSERT_WITH_MESSAGE(b.size() <= n, "oversize b in quorem");
  if (b.size() < n)
    return 0;
  sx = S.words();
  sxe = sx + --n;
  bx = b.words();
  bxe = bx + n;
  q = *bxe / (*sxe + 1); /* ensure q <= true quotient */
  ASSERT_WITH_MESSAGE(q <= 9, "oversized quotient in quorem");
  if (q) {
    borrow = 0;
    carry = 0;
    do {
#ifdef USE_LONG_LONG
      ys = *sx++ * (unsigned long long)q + carry;
      carry = ys >> 32;
      y = *bx - (ys & 0xffffffffUL) - borrow;
      borrow = y >> 32 & (uint32_t)1;
      *bx++ = (uint32_t)y & 0xffffffffUL;
#else
      si = *sx++;
      ys = (si & 0xffff) * q + carry;
      zs = (si >> 16) * q + (ys >> 16);
      carry = zs >> 16;
      y = (*bx & 0xffff) - (ys & 0xffff) - borrow;
      borrow = (y & 0x10000) >> 16;
      z = (*bx >> 16) - (zs & 0xffff) - borrow;
      borrow = (z & 0x10000) >> 16;
      bx = storeInc(bx, z, y);
#endif
    } while (sx <= sxe);
    if (!*bxe) {
      bx = b.words();
      while (--bxe > bx && !*bxe)
        --n;
      b.resize(n);
    }
  }
  if (cmp(b, S) >= 0) {
    q++;
    borrow = 0;
    carry = 0;
    bx = b.words();
    sx = S.words();
    do {
#ifdef USE_LONG_LONG
      ys = *sx++ + carry;
      carry = ys >> 32;
      y = *bx - (ys & 0xffffffffUL) - borrow;
      borrow = y >> 32 & (uint32_t)1;
      *bx++ = (uint32_t)y & 0xffffffffUL;
#else
      si = *sx++;
      ys = (si & 0xffff) + carry;
      zs = (si >> 16) + (ys >> 16);
      carry = zs >> 16;
      y = (*bx & 0xffff) - (ys & 0xffff) - borrow;
      borrow = (y & 0x10000) >> 16;
      z = (*bx >> 16) - (zs & 0xffff) - borrow;
      borrow = (z & 0x10000) >> 16;
      bx = storeInc(bx, z, y);
#endif
    } while (sx <= sxe);
    bx = b.words();
    bxe = bx + n;
    if (!*bxe) {
      while (--bxe > bx && !*bxe)
        --n;
      b.resize(n);
    }
  }
  return q;
}

/* dtoa for IEEE arithmetic (dmg): convert double to ASCII string.
 *
 * Inspired by "How to Print Floating-Point Numbers Accurately" by
 * Guy L. Steele, Jr. and Jon L. White [Proc. ACM SIGPLAN '90, pp. 112-126].
 *
 * Modifications:
 *    1. Rather than iterating, we use a simple numeric overestimate
 *       to determine k = floor(log10(d)).  We scale relevant
 *       quantities using O(log2(k)) rather than O(k) multiplications.
 *    2. For some modes > 2 (corresponding to ecvt and fcvt), we don't
 *       try to generate digits strictly left to right.  Instead, we
 *       compute with fewer bits and propagate the carry if necessary
 *       when rounding the final digit up.  This is often faster.
 *    3. Under the assumption that input will be rounded nearest,
 *       mode 0 renders 1e23 as 1e23 rather than 9.999999999999999e22.
 *       That is, we allow equality in stopping tests when the
 *       round-nearest rule will give the same floating-point value
 *       as would satisfaction of the stopping test with strict
 *       inequality.
 *    4. We remove common factors of powers of 2 from relevant
 *       quantities.
 *    5. When converting floating-point integers less than 1e16,
 *       we use floating-point arithmetic rather than resorting
 *       to multiple-precision integers.
 *    6. When asked to produce fewer than 15 digits, we first try
 *       to get by with floating-point arithmetic; we resort to
 *       multiple-precision integer arithmetic only if we cannot
 *       guarantee that the floating-point calculation has given
 *       the correctly rounded result.  For k requested digits and
 *       "uniformly" distributed input, the probability is
 *       something like 10^(k-15) that we must resort to the int32_t
 *       calculation.
 *
 * Note: 'leftright' translates to 'generate shortest possible string'.
 */
template <bool roundingNone,
          bool roundingSignificantFigures,
          bool roundingDecimalPlaces,
          bool leftright>
void dtoa(DtoaBuffer result,
          double dd,
          int ndigits,
          bool& signOut,
          int& exponentOut,
          unsigned& precisionOut) {
  // Exactly one rounding mode must be specified.
  ASSERT(roundingNone + roundingSignificantFigures + roundingDecimalPlaces ==
         1);
  // roundingNone only allowed (only sensible?) with leftright set.
  ASSERT(!roundingNone || leftright);

  ASSERT(std::isfinite(dd));

  int bbits, b2, b5, be, dig, i, ieps, ilim = 0, ilim0, ilim1 = 0, j, j1, k, k0,
                                       k_check, m2, m5, s2, s5, spec_case;
  int32_t L;
  int denorm;
  uint32_t x;
  BigInt b, delta, mlo, mhi, S;
  U d2, eps, u;
  double ds;
  char* s;
  char* s0;

  u.d = dd;

  /* Infinity or NaN */
  ASSERT((word0(&u) & Exp_mask) != Exp_mask);

  // JavaScript toString conversion treats -0 as 0.
  if (!dval(&u)) {
    signOut = false;
    exponentOut = 0;
    precisionOut = 1;
    result[0] = '0';
    result[1] = '\0';
    return;
  }

  if (word0(&u) & Sign_bit) {
    signOut = true;
    word0(&u) &= ~Sign_bit;  // clear sign bit
  } else
    signOut = false;

  d2b(b, &u, &be, &bbits);
  if ((i = (int)(word0(&u) >> Exp_shift1 & (Exp_mask >> Exp_shift1)))) {
    dval(&d2) = dval(&u);
    word0(&d2) &= Frac_mask1;
    word0(&d2) |= Exp_11;

    /* log(x)    ~=~ log(1.5) + (x-1.5)/1.5
     * log10(x)     =  log(x) / log(10)
     *        ~=~ log(1.5)/log(10) + (x-1.5)/(1.5*log(10))
     * log10(d) = (i-Bias)*log(2)/log(10) + log10(d2)
     *
     * This suggests computing an approximation k to log10(d) by
     *
     * k = (i - Bias)*0.301029995663981
     *    + ( (d2-1.5)*0.289529654602168 + 0.176091259055681 );
     *
     * We want k to be too large rather than too small.
     * The error in the first-order Taylor series approximation
     * is in our favor, so we just round up the constant enough
     * to compensate for any error in the multiplication of
     * (i - Bias) by 0.301029995663981; since |i - Bias| <= 1077,
     * and 1077 * 0.30103 * 2^-52 ~=~ 7.2e-14,
     * adding 1e-13 to the constant term more than suffices.
     * Hence we adjust the constant term to 0.1760912590558.
     * (We could get a more accurate k by invoking log10,
     *  but this is probably not worthwhile.)
     */

    i -= Bias;
    denorm = 0;
  } else {
    /* d is denormalized */

    i = bbits + be + (Bias + (P - 1) - 1);
    x = (i > 32) ? (word0(&u) << (64 - i)) | (word1(&u) >> (i - 32))
                 : word1(&u) << (32 - i);
    dval(&d2) = x;
    word0(&d2) -= 31 * Exp_msk1; /* adjust exponent */
    i -= (Bias + (P - 1) - 1) + 1;
    denorm = 1;
  }
  ds = (dval(&d2) - 1.5) * 0.289529654602168 + 0.1760912590558 +
       (i * 0.301029995663981);
  k = (int)ds;
  if (ds < 0. && ds != k)
    k--; /* want k = floor(ds) */
  k_check = 1;
  if (k >= 0 && k <= Ten_pmax) {
    if (dval(&u) < tens[k])
      k--;
    k_check = 0;
  }
  j = bbits - i - 1;
  if (j >= 0) {
    b2 = 0;
    s2 = j;
  } else {
    b2 = -j;
    s2 = 0;
  }
  if (k >= 0) {
    b5 = 0;
    s5 = k;
    s2 += k;
  } else {
    b2 -= k;
    b5 = -k;
    s5 = 0;
  }

  if (roundingNone) {
    ilim = ilim1 = -1;
    i = 18;
    ndigits = 0;
  }
  if (roundingSignificantFigures) {
    if (ndigits <= 0)
      ndigits = 1;
    ilim = ilim1 = i = ndigits;
  }
  if (roundingDecimalPlaces) {
    i = ndigits + k + 1;
    ilim = i;
    ilim1 = i - 1;
    if (i <= 0)
      i = 1;
  }

  s = s0 = result;

  if (ilim >= 0 && ilim <= Quick_max) {
    /* Try to get by with floating-point arithmetic. */

    i = 0;
    dval(&d2) = dval(&u);
    k0 = k;
    ilim0 = ilim;
    ieps = 2; /* conservative */
    if (k > 0) {
      ds = tens[k & 0xf];
      j = k >> 4;
      if (j & Bletch) {
        /* prevent overflows */
        j &= Bletch - 1;
        dval(&u) /= bigtens[n_bigtens - 1];
        ieps++;
      }
      for (; j; j >>= 1, i++) {
        if (j & 1) {
          ieps++;
          ds *= bigtens[i];
        }
      }
      dval(&u) /= ds;
    } else if ((j1 = -k)) {
      dval(&u) *= tens[j1 & 0xf];
      for (j = j1 >> 4; j; j >>= 1, i++) {
        if (j & 1) {
          ieps++;
          dval(&u) *= bigtens[i];
        }
      }
    }
    if (k_check && dval(&u) < 1. && ilim > 0) {
      if (ilim1 <= 0)
        goto fastFailed;
      ilim = ilim1;
      k--;
      dval(&u) *= 10.;
      ieps++;
    }
    dval(&eps) = (ieps * dval(&u)) + 7.;
    word0(&eps) -= (P - 1) * Exp_msk1;
    if (!ilim) {
      S.clear();
      mhi.clear();
      dval(&u) -= 5.;
      if (dval(&u) > dval(&eps))
        goto oneDigit;
      if (dval(&u) < -dval(&eps))
        goto noDigits;
      goto fastFailed;
    }
    if (leftright) {
      /* Use Steele & White method of only
       * generating digits needed.
       */
      dval(&eps) = (0.5 / tens[ilim - 1]) - dval(&eps);
      for (i = 0;;) {
        L = (long int)dval(&u);
        dval(&u) -= L;
        *s++ = '0' + (int)L;
        if (dval(&u) < dval(&eps))
          goto ret;
        if (1. - dval(&u) < dval(&eps))
          goto bumpUp;
        if (++i >= ilim)
          break;
        dval(&eps) *= 10.;
        dval(&u) *= 10.;
      }
    } else {
      /* Generate ilim digits, then fix them up. */
      dval(&eps) *= tens[ilim - 1];
      for (i = 1;; i++, dval(&u) *= 10.) {
        L = (int32_t)(dval(&u));
        if (!(dval(&u) -= L))
          ilim = i;
        *s++ = '0' + (int)L;
        if (i == ilim) {
          if (dval(&u) > 0.5 + dval(&eps))
            goto bumpUp;
          if (dval(&u) < 0.5 - dval(&eps)) {
            while (*--s == '0') {
            }
            s++;
            goto ret;
          }
          break;
        }
      }
    }
  fastFailed:
    s = s0;
    dval(&u) = dval(&d2);
    k = k0;
    ilim = ilim0;
  }

  /* Do we have a "small" integer? */

  if (be >= 0 && k <= Int_max) {
    /* Yes. */
    ds = tens[k];
    if (ndigits < 0 && ilim <= 0) {
      S.clear();
      mhi.clear();
      if (ilim < 0 || dval(&u) <= 5 * ds)
        goto noDigits;
      goto oneDigit;
    }
    for (i = 1;; i++, dval(&u) *= 10.) {
      L = (int32_t)(dval(&u) / ds);
      dval(&u) -= L * ds;
      *s++ = '0' + (int)L;
      if (!dval(&u)) {
        break;
      }
      if (i == ilim) {
        dval(&u) += dval(&u);
        if (dval(&u) > ds || (dval(&u) == ds && (L & 1))) {
        bumpUp:
          while (*--s == '9')
            if (s == s0) {
              k++;
              *s = '0';
              break;
            }
          ++*s++;
        }
        break;
      }
    }
    goto ret;
  }

  m2 = b2;
  m5 = b5;
  mhi.clear();
  mlo.clear();
  if (leftright) {
    i = denorm ? be + (Bias + (P - 1) - 1 + 1) : 1 + P - bbits;
    b2 += i;
    s2 += i;
    i2b(mhi, 1);
  }
  if (m2 > 0 && s2 > 0) {
    i = m2 < s2 ? m2 : s2;
    b2 -= i;
    m2 -= i;
    s2 -= i;
  }
  if (b5 > 0) {
    if (leftright) {
      if (m5 > 0) {
        pow5mult(mhi, m5);
        mult(b, mhi);
      }
      if ((j = b5 - m5))
        pow5mult(b, j);
    } else
      pow5mult(b, b5);
  }
  i2b(S, 1);
  if (s5 > 0)
    pow5mult(S, s5);

  /* Check for special case that d is a normalized power of 2. */

  spec_case = 0;
  if ((roundingNone || leftright) && (!word1(&u) && !(word0(&u) & Bndry_mask) &&
                                      word0(&u) & (Exp_mask & ~Exp_msk1))) {
    /* The special case */
    b2 += Log2P;
    s2 += Log2P;
    spec_case = 1;
  }

  /* Arrange for convenient computation of quotients:
   * shift left if necessary so divisor has 4 leading 0 bits.
   *
   * Perhaps we should just compute leading 28 bits of S once
   * and for all and pass them and a shift to quorem, so it
   * can do shifts and ors to compute the numerator for q.
   */
  if ((i = ((s5 ? 32 - hi0bits(S.words()[S.size() - 1]) : 1) + s2) & 0x1f))
    i = 32 - i;
  if (i > 4) {
    i -= 4;
    b2 += i;
    m2 += i;
    s2 += i;
  } else if (i < 4) {
    i += 28;
    b2 += i;
    m2 += i;
    s2 += i;
  }
  if (b2 > 0)
    lshift(b, b2);
  if (s2 > 0)
    lshift(S, s2);
  if (k_check) {
    if (cmp(b, S) < 0) {
      k--;
      multadd(b, 10, 0); /* we botched the k estimate */
      if (leftright)
        multadd(mhi, 10, 0);
      ilim = ilim1;
    }
  }
  if (ilim <= 0 && roundingDecimalPlaces) {
    if (ilim < 0)
      goto noDigits;
    multadd(S, 5, 0);
    // For IEEE-754 unbiased rounding this check should be <=, such that 0.5
    // would flush to zero.
    if (cmp(b, S) < 0)
      goto noDigits;
    goto oneDigit;
  }
  if (leftright) {
    if (m2 > 0)
      lshift(mhi, m2);

    /* Compute mlo -- check for special case
     * that d is a normalized power of 2.
     */

    mlo = mhi;
    if (spec_case)
      lshift(mhi, Log2P);

    for (i = 1;; i++) {
      dig = quorem(b, S) + '0';
      /* Do we yet have the shortest decimal string
       * that will round to d?
       */
      j = cmp(b, mlo);
      diff(delta, S, mhi);
      j1 = delta.sign ? 1 : cmp(b, delta);
#ifdef DTOA_ROUND_BIASED
      if (j < 0 || !j) {
#else
      // FIXME: ECMA-262 specifies that equidistant results round away from
      // zero, which probably means we shouldn't be on the unbiased code path
      // (the (word1(&u) & 1) clause is looking highly suspicious). I haven't
      // yet understood this code well enough to make the call, but we should
      // probably be enabling DTOA_ROUND_BIASED. I think the interesting corner
      // case to understand is probably "Math.pow(0.5, 24).toString()".
      // I believe this value is interesting because I think it is precisely
      // representable in binary floating point, and its decimal representation
      // has a single digit that Steele & White reduction can remove, with the
      // value 5 (thus equidistant from the next numbers above and below).
      // We produce the correct answer using either codepath, and I don't as
      // yet understand why. :-)
      if (!j1 && !(word1(&u) & 1)) {
        if (dig == '9')
          goto round9up;
        if (j > 0)
          dig++;
        *s++ = dig;
        goto ret;
      }
      if (j < 0 || (!j && !(word1(&u) & 1))) {
#endif
        if ((b.words()[0] || b.size() > 1) && (j1 > 0)) {
          lshift(b, 1);
          j1 = cmp(b, S);
          // For IEEE-754 round-to-even, this check should be (j1 > 0 || (!j1 &&
          // (dig & 1))), but ECMA-262 specifies that equidistant values (e.g.
          // (.5).toFixed()) should be rounded away from zero.
          if (j1 >= 0) {
            if (dig == '9')
              goto round9up;
            dig++;
          }
        }
        *s++ = dig;
        goto ret;
      }
      if (j1 > 0) {
        if (dig == '9') { /* possible if i == 1 */
        round9up:
          *s++ = '9';
          goto roundoff;
        }
        *s++ = dig + 1;
        goto ret;
      }
      *s++ = dig;
      if (i == ilim)
        break;
      multadd(b, 10, 0);
      multadd(mlo, 10, 0);
      multadd(mhi, 10, 0);
    }
  } else {
    for (i = 1;; i++) {
      *s++ = dig = quorem(b, S) + '0';
      if (!b.words()[0] && b.size() <= 1)
        goto ret;
      if (i >= ilim)
        break;
      multadd(b, 10, 0);
    }
  }

  /* Round off last digit */

  lshift(b, 1);
  j = cmp(b, S);
  // For IEEE-754 round-to-even, this check should be (j > 0 || (!j && (dig &
  // 1))), but ECMA-262 specifies that equidistant values (e.g. (.5).toFixed())
  // should be rounded away from zero.
  if (j >= 0) {
  roundoff:
    while (*--s == '9')
      if (s == s0) {
        k++;
        *s++ = '1';
        goto ret;
      }
    ++*s++;
  } else {
    while (*--s == '0') {
    }
    s++;
  }
  goto ret;
noDigits:
  exponentOut = 0;
  precisionOut = 1;
  result[0] = '0';
  result[1] = '\0';
  return;
oneDigit:
  *s++ = '1';
  k++;
  goto ret;
ret:
  ASSERT(s > result);
  *s = 0;
  exponentOut = k;
  precisionOut = s - result;
}

void dtoa(DtoaBuffer result,
          double dd,
          bool& sign,
          int& exponent,
          unsigned& precision) {
  // flags are roundingNone, leftright.
  dtoa<true, false, false, true>(result, dd, 0, sign, exponent, precision);
}

void dtoaRoundSF(DtoaBuffer result,
                 double dd,
                 int ndigits,
                 bool& sign,
                 int& exponent,
                 unsigned& precision) {
  // flag is roundingSignificantFigures.
  dtoa<false, true, false, false>(result, dd, ndigits, sign, exponent,
                                  precision);
}

void dtoaRoundDP(DtoaBuffer result,
                 double dd,
                 int ndigits,
                 bool& sign,
                 int& exponent,
                 unsigned& precision) {
  // flag is roundingDecimalPlaces.
  dtoa<false, false, true, false>(result, dd, ndigits, sign, exponent,
                                  precision);
}

const char* numberToString(double d, NumberToStringBuffer buffer) {
  double_conversion::StringBuilder builder(buffer, NumberToStringBufferLength);
  const double_conversion::DoubleToStringConverter& converter =
      double_conversion::DoubleToStringConverter::EcmaScriptConverter();
  converter.ToShortest(d, &builder);
  return builder.Finalize();
}

static inline const char* formatStringTruncatingTrailingZerosIfNeeded(
    NumberToStringBuffer buffer,
    double_conversion::StringBuilder& builder) {
  size_t length = builder.position();
  size_t decimalPointPosition = 0;
  for (; decimalPointPosition < length; ++decimalPointPosition) {
    if (buffer[decimalPointPosition] == '.')
      break;
  }

  // No decimal seperator found, early exit.
  if (decimalPointPosition == length)
    return builder.Finalize();

  size_t truncatedLength = length - 1;
  for (; truncatedLength > decimalPointPosition; --truncatedLength) {
    if (buffer[truncatedLength] != '0')
      break;
  }

  // No trailing zeros found to strip.
  if (truncatedLength == length - 1)
    return builder.Finalize();

  // If we removed all trailing zeros, remove the decimal point as well.
  if (truncatedLength == decimalPointPosition) {
    ASSERT(truncatedLength > 0);
    --truncatedLength;
  }

  // Truncate the StringBuilder, and return the final result.
  builder.SetPosition(truncatedLength + 1);
  return builder.Finalize();
}

const char* numberToFixedPrecisionString(double d,
                                         unsigned significantFigures,
                                         NumberToStringBuffer buffer,
                                         bool truncateTrailingZeros) {
  // Mimic String::format("%.[precision]g", ...), but use dtoas rounding
  // facilities. "g": Signed value printed in f or e format, whichever is more
  // compact for the given value and precision. The e format is used only when
  // the exponent of the value is less than –4 or greater than or equal to the
  // precision argument. Trailing zeros are truncated, and the decimal point
  // appears only if one or more digits follow it. "precision": The precision
  // specifies the maximum number of significant digits printed.
  double_conversion::StringBuilder builder(buffer, NumberToStringBufferLength);
  const double_conversion::DoubleToStringConverter& converter =
      double_conversion::DoubleToStringConverter::EcmaScriptConverter();
  converter.ToPrecision(d, significantFigures, &builder);
  if (!truncateTrailingZeros)
    return builder.Finalize();
  return formatStringTruncatingTrailingZerosIfNeeded(buffer, builder);
}

const char* numberToFixedWidthString(double d,
                                     unsigned decimalPlaces,
                                     NumberToStringBuffer buffer) {
  // Mimic String::format("%.[precision]f", ...), but use dtoas rounding
  // facilities. "f": Signed value having the form [ – ]dddd.dddd, where dddd is
  // one or more decimal digits. The number of digits before the decimal point
  // depends on the magnitude of the number, and the number of digits after the
  // decimal point depends on the requested precision. "precision": The
  // precision value specifies the number of digits after the decimal point. If
  // a decimal point appears, at least one digit appears before it. The value is
  // rounded to the appropriate number of digits.
  double_conversion::StringBuilder builder(buffer, NumberToStringBufferLength);
  const double_conversion::DoubleToStringConverter& converter =
      double_conversion::DoubleToStringConverter::EcmaScriptConverter();
  converter.ToFixed(d, decimalPlaces, &builder);
  return builder.Finalize();
}

namespace Internal {

double parseDoubleFromLongString(const UChar* string,
                                 size_t length,
                                 size_t& parsedLength) {
  Vector<LChar> conversionBuffer(length);
  for (size_t i = 0; i < length; ++i)
    conversionBuffer[i] = isASCII(string[i]) ? string[i] : 0;
  return parseDouble(conversionBuffer.data(), length, parsedLength);
}

}  // namespace Internal

}  // namespace WTF
